Class 8 Science Question Answers - Pollution of Air and Water (Old Syllabus)

Q1: Why it is dangerous to burn polymers?

Ans: When polymers such as plastics are burned carbon containing gases are released. During the burning process, the carbon combines with oxygen present in the atmosphere & forms oxides of carbon. These gases have been linked with global warming, depletion of the ozone layer, acid rain, etc.
Q2: What is the cause of acid rain?

Ans: Oxides of nitrogen, sulphur, carbon produced by combustion of coal, petroleum, etc. dissolve in atmospheric water vapour. They form their corresponding acids like nitric acid, sulphuric acid, etc., and reach the earth's surface as acid rain.
Q3: How does industry pollute the environment?

Ans: Factories pollute the air by pumping out chemicals that are harmful for all living things. Factories can pollute the environment through thermal pollution, chemical pollution, air pollution, noise pollution.
Q4: What steps should be taken to minimise air pollution?

Ans: Air pollution cab be reduced by adopting following ways:

1. Reduce the use of car and other vehicles as these are the significant source of air pollution, so switching to a more gas-efficient vehicle will be a big help. Taking public transport to work rather than driving will reduces the number of carbon dioxide into the air. Using eco-friendly fuels in vehicles like CNG can also be beneficial.

2. Reduce Waste: Manufacturing of unnecessary or disposable goods often produces air pollution, so reduced purchasing of disposables will help. In general, follow the solid waste mantra - "Reduce, Reuse, Repair, And Recycle" - and this will reduce air pollution as well from transporting, treating, or disposing of unnecessary wastes.

3. Eliminate Toxic Chemical Use at Home --- A surprising number of household or home shop chemicals are toxic and volatile. Many release vapours into the air, inside the home and out. This can be serious health threat to your family, and contributes to community-wide levels of air pollutants.

4. Plant leafy trees and shrubs --- Deciduous trees and shrubs (the kinds that drop leaves in the fall) are excellent air filters to help reduce smog and cool the air on hot summer days.
Q5: What are factory fumes?

Ans: Nitrous Oxides (NO, NO2 and N2O), Sulphur Dioxide, Carbon Dioxide and Carbon Monoxide are the famous ones, depending on the reactions that are taking place in the factory.
Q6: What are the harmful effects of acid rain?

Ans: Harmful effects of acid rain are as follows:
1. It irritates eyes and skin of human beings.

2. It inhibits germination and growth of seedlings.

3. It changes the fertility of the soil, destroys plants and aquatic life.

4. It causes corrosion of many buildings, bridges, etc.
Q7: How acid rain does effects the environment?

Ans: Acid rain affects the environment in several ways:

1. It can leach nutrients from the soil making then unavailable to plant life.

2. It can affect the growth of plants as many plants have a specific soil pH for optimum growth

3. Acid precipitation can change the ionic balance in clayey soils affecting their structure.

4. In some soils acid precipitation may free up metals (e.g. lead) in the soil that can be taken up by the plants and contaminate the associated seeds or fruit.

5. It can affect fish and amphibians by reducing the pH of the water impacting their health and breeding success.
Q8: How acid rain does effects water ecosystem?

Ans: Together biological organisms and the environment in which they live are called an ecosystem. The plants and animals living within an ecosystem are highly interdependent. For example, frogs may tolerate relatively high levels of acidity, but if they eat insects like the mayfly, they may be affected because part of their food supply may disappear. Because of the connections between the many fish, plants, and other organisms living in an aquatic ecosystem, changes in pH or aluminium levels affect biodiversity as well. Thus, as lakes and streams become more acidic, the numbers and types of fish and other aquatic plants and animals that live in these waters decrease.
Q9: What are the causes of increasing amount of carbon dioxide in air?
Ans: Human activities are the main reason for increasing the amount of carbon dioxide (CO₂) in the atmosphere. The major sources of human emissions are the burning of fossil fuels such as coal, oil and natural gas for industry, driving our transport, heating our homes and generating electricity. Another factor is deforestation which increases the amount of carbon dioxide in the atmosphere, because new trees are not allowed to replace those removed.
Q10: Explain the three R principles to reduce pollution.

Ans: The three R principle includes recycle, reuse, and reduce of the available resources
Q11: Define water pollution.

Ans: Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater caused by human activities, which can be harmful to organisms and plants which live in these water bodies.
Q12: List three major man-made source of air pollution.

Ans: Three major man-made source of air pollution are: Industrialisation, Urbanisation and Automobiles
Q13: How does environment problem effect people health?

Ans: Air pollution is a significant risk factor for multiple health conditions including respiratory infections, heart disease, and lung cancer. The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions.
Q14: How does burning of fossil fuels effects carbon dioxide level in the atmosphere?

Ans: Fossil fuels contain carbon, hydrogen, Nitrogen, Oxygen and some other elements. But the majority is Carbon. So when such fuels burn they combine with the Oxygen and Nitrogen in air to form Carbon dioxide, Nitrogen oxides etc. Even though Carbon monoxide is also formed, since they get converted to carbon dioxide when combustion gets completed. Any form of carbon when burns produce carbon dioxide.
Q15: What gastrointestinal problems may occur with antihistamine use?

Ans: Gastrointestinal problems include increased appetite, decreased appetite, nausea, vomiting, diarrhoea, and constipation.
Q16: Why acid rain and rust a harmful effect?

Ans: Acid rain and rust are harmful because it contains harmful gases like sulphuric acid etc. mainly sulphur gases because of this harmful gases when they reach the atmosphere when it rains it forms acid rain as the harmful gases mix with the atmosphere .This acid rain will affect plants, animals humans and all living organism. The acid mainly occurs at industrial areas because of these harmful gases which are released by the industrial effluents, they are definitely harmful to the atmosphere.
Q17: How does water get polluted?

Ans: It gets polluted by acid rain, oil spills, litter, insecticide mixing with fertilizers etc. The emission of waste heat from an electric generating station into a lake, causing common change through their stress. The discharge of nutrients containing sewer wastes, in a water body causing eutrophication.
Q18: Explain Ganga Action Plan.

Ans: The Ganga action plan was, launched by Sri Rajeev Gandhi, the then Prime Minister of India on 14 Jan. 1985 with the main objective of pollution abatement, to improve the water quality by Interception, Diversion and treatment of domestic sewage and present toxic and industrial chemical wastes from identified grossly polluting units entering in to the river. The other objectives of the Ganga Action Plan are as under.

• Control of non-point pollution from agricultural runoff, human defecation, cattle wallowing and throwing of unburnt and half burnt bodies into the river.
• Research and Development to conserve the biotic, diversity of the river to augment its productivity.
• New technology of sewage treatment like Up-flow Anaerobic Sludge Blanket (UASB) and sewage treatment through afforestation has been successfully developed.
• Rehabilitation of soft-shelled turtles for pollution abatement of river have been demonstrated and found useful.
• Resource recovery options like production of methane for energy generation and use of aquaculture for revenue generation have been demonstrated.
• To act as trend setter for taking up similar action plans in other grossly polluted stretches in other rivers.

Q19: How the disposal of garbage etc. would affects the living organisms in the river?

Ans: Disposal of garbage can affect badly the living organisms present in water, they will not be able to survive in water and may die.
Q20: What are the different ways in which water get contaminated?
Ans: Whenever harmful substances such as sewage, toxic chemicals, silt etc. get mixed with water, the water becomes polluted. Water get contaminated by the addition of agricultural chemicals like pesticides and fertilizers , these chemicals get carried away to the water bodies due to rains and flood which lead to water pollution, apart from this industrial wastes like harmful chemical wastes also causes water pollution. Sewage wastes like waste material from kitchens, toilets and laundry sources are also responsible for contaminating water.
Q21: What are the differences between pure water and polluted water?

Ans:

Q22: Describe greenhouse effects.

Ans: The greenhouse effect is the process which leads to increase in average earth's temperature. That is the global warming. It results because of the greenhouse gases like water vapour, carbon dioxide, nitrous oxide, and methane, trap energy from the sun. When solar radiation reaches earth some of these radiations are absorbed by earth and rest are released back to the atmosphere. Greenhouse gases trap these radiations and do not allow them to go back. This helps in keeping earth warm and in survival of human beings. However an increase in amount of greenhouse gases can lead to excessive increase in earth's temperature leading to global warming.